Japanese pear tree Gold Nijisseiki

ABSTRACT

The new and distinct cultivar relates to a Japanese pear tree that has a strong resistance to black spot disease and substantially has the same excellent qualities of &#34;Nijisseiki&#34; as a Japanese pear cultivar. This pear tree bears a yellowish green fruit, is moderately sweet and acidic, and has a good taste that is suitable for desserts.

BACKGROUND OF THE CULTIVAR

The present invention relates to a new and distinct cultivar of Japanesepear tree (Pyrus pyrifiolia), and, particularly, to the tree bearingfruit with a yellowish-green skin, having characteristics substantiallythe same as those of "Nijisseiki", but having a significantly strongresistance to black spot disease.

In Japan, "Nijisseiki", which is considered a chance seedling, is anexcellent cultivar that is gradually increasing in popularity so as tocomprise about 40 percent of the total cultivation area of the Japanesepear tree to date. It has, however, a severe shortcoming in that"Nijisseiki" has a high susceptibility to black spot disease, and thusit is only capable of being cultivated on a large scale in an areahaving little rain from spring through summer.

The black spot disease is developed on the leaf, stem and the fruit of"Nijisseiki" tree, in particular, the young fruit is associated with theformation of black and rounded lesions, and cracking.

One objective of the present inventors is to provide an improvedcultivar of the pear fruit tree having a strong resistance to black spotdisease, while also having the excellent characteristics of the"Nijisseiki".

ORIGIN AND ASEXUAL REPRODUCTION OF THE CULTIVAR

The new cultivar of Japanese pear tree was derived from "Nijisseiki" bymutation breeding. In 1962, nursery stocks of "Nijisseiki" were plantedat a gamma field of the Institute of Radiation Breeding NationalInstitute of Agrobiological Resources, Ministry of Agriculture, Forestryand Fisheries, Omiya-machi, Naka-gun, Ibaraki, Japan, and have beencontinuously exposed to γ-rays hitherto. In 1981, the amount offungicide sprayed on the trees was reduced and one of the treesdeveloped a branch devoid of the symptoms associated with black spotdisease. It has been confirmed that the said bough has a significantlystrong resistance to black spot disease compared to "Nijisseiki". Thebranch was top-grafted on rootstocks to subject same to a localadaptability test at the fields of each prefectural experimental stationlocated in Tottori, which is the main production region of "Nijisseiki",Nagano, Fukushima, and the like, since 1986.

As a result, the trees bore fruit for the first time in 1988, and it wasfound that the trees have a significantly strong resistance to blackspot disease compared to "Nijisseiki" while also displaying theexcellent characteristics of the Nijisseiki. For instance, in 1989, thetrees had not developed lesions of black spot disease on the leaves,stem or fruit based upon the susceptibility to black spot disease fieldtests. In the past in trees that had black spot disease, 90 percent ofthe total leaves of "Nijisseiki" were damaged, but the value for thisnew cultivar tree was only 5 percent at the Nagano-ken NanshinAgricultural Experimental Station, and 6.9 percent at the Gunma-kenHorticultural Experimental Station.

The present inventors named the new tree "Gold Nijisseiki".

This new and distinct cultivar of Japanese pear tree "Gold Nijisseiki"was asexually reproduced by grafting, at the various PrefecturalExperimental Stations, and confirmed the homogeneity and stabilitythereof.

An application for this new cultivar of Japanese pear tree "GoldNijisseiki" under the Seeds and Seedlings Law of Japan was filed on Mar.26, 1990, and registered under Number 2932 on Dec. 16, 1991.

In the following description, the color-coding is in accordance with theInter-Society Color Council-National Bureu of Standards (ISCC-NBS ColorName).

The new cultivar of Japanese pear tree according to the presentinvention was developed inadvertently from "Nijisseiki" by mutationbreeding using γ-rays as a mutagen. As described above, "Nijisseiki"which is the parent cultivar, was obtained as a chance seedling before1900, and was widely cultivated in Japan. The main characteristics ofthe parent cultivar are as follows:

Tree:

Vigor.--Habit of branches is medium. The unpruned tree may have a heightof about 7 m and a width of about 4 m when 15 years old. When the treewas grafted on a root stock, which is a seedling stock of Japanese pear,and cultivated for 10 years, a vegetative shoot of the tree extended to70-80 cm per year.

Spur.--Easy to maintain. The number of spurs is 12 per meter of branch.

Predominance of axillary flower bud.--Few(5.8%).

Time of bud break.--Medium, around April 9th, at Ibaraki prefecture,Japan.

Production.--High productivity.

Cross-compatibility.--Cross-compatible with, e.g., "Chojuro", "Kosui".The tree is self-incompatible and is manually pollinated. The fruit setpercentage is 90-100%.

Bark.--The bark texture of the new and old wood is hard, and the bark ofa 10 year old tree may be cracked. The lenticels of the new and old woodare medium, and density thereof is medium (110/10 cm).

Branches (shoot):

Length.--Medium, about 78.8 cm at one year old.

Thickness.--Stout, about 8.78 mm.

Length of internode.--Short, about 4.3 cm.

Color.--Light green brown (ISCC-NBS, Strong Yellowish Brown).

Density of pubescence.--High.

Angle between leaf bud and shoot.--Medium, about 26.8°.

Leaves:

Shape.--Oval.

Size.--Medium (11.1 cm×6.7 cm).

Color.--Dark Green (ISCC-NBS, Dark Green).

Length of petiole.--Short, about 2.6 cm.

Thickness of petiole.--Medium, about 2.4 mm.

Color of young leaves.--Brown (ISCC-NBS, Deep Reddish Brown).

Density of pubescence of young leaves.--High.

Flowers:

Flower number in a flower cluster.--Slightly more than medium, about10.25 on average.

Size.--Medium, about 3.4 cm.

Color.--Light pink (ISCC-NBS, Light Pink) calyx, coloration at bloomingfades to pure white (ISCC-NBS, Whilte) with flower opening.

Shape of petals.--Round.

Notch of margin of petals.--Medium.

Number of petals.--Slightly more than medium, 5.56 pieces on average.

Color of anther.--Strong red (ISCC-NBS, Strong Red).

Number of stamens.--Slightly more than medium, 27.1 on average.

Number of pollen.--Much.

Flowering time.--Middle in the season.

Flowering data and full bloom stage.--April 20th and April 24th at theInstitute of Radiation Breeding, NIAR, on average from 1987 to 1989.

Fruit:

Size.--323 g on average.

Shape.--Round.

Color of skin (unbagged fruit).--Yellowish green (ISCC-NBS, Light YellowGreen).

Calyx perpetual fruit.--Absent.

Size of dot.--Medium.

Density of dot.--Medium.

Color of flesh.--Yellowish white (ISCC-NBS, Pale Greenish Yellow).

Flesh.--Soft and juicy. The firmness is about 4.26 lbs. according toMagness-Teller's hardness meter index. The fruit can be stored at20°-25° C. for 15 days.

Length of peduncle.--Medium, 3.6 cm on average.

Thickness of peduncle.--Stout, 4.3 mm on average.

Color of peduncle.--Dull green (ISCC-NBS, Moderate Yellowish Green)

Color of dot.--Dull Yellow (ISCC-NBS, Moderate Yellow).

Color of core.--Yellowish White (ISCC-NBS, Yellowish White).

Shape of core.--Short conical.

Size of core.--Medium (core/fruit=40/87, at transverse diameter).

Seed cells.--5 cells per fruit, about 1.7 seeds per cell, 4-5 seeds perwell shaped fruit.

Size of seeds.--Medium, 8.9 mm×5.9 mm on average.

Shape of seeds.--Oval.

Taste.--Moderate sweetness, the sugar content of the fruit juice isabout 10.9%, a medium acidity, pH 4.8, and no astringency. Although thetaste of the fruit at skin/flesh interface cannot be distinguished, thetaste of the core flesh tissues surrounding the seed cells has slightlyhigher acidity than other parts.

Bagged.--The bagged fruit has a slightly fine appearance compared tofruit that has not been bagged, but the latter is less than the formerin sweetness. Color of both are not distinguishable from each other, butin the unbagged fruit, cork spots are slightly more apparent than in thebagged fruit.

Maturity.--Ripening middle in the season, e.g., September 16-25th at theInstitute of Radiation Breeding, NIAR.

Use.--Suitable for dessert.

Keeping quality.--Can be kept for about 15 days at 20°-25° C.

Resistance to diseases: Has a high susceptibility to black spot diseaseand susceptibility to pear necrotic spot virus, but has minorsusceptibility to pear scab. The tree is not susceptible to pear canker.

Cold resistant: Almost the same as that of other Japanese pears.

Core breakdown: Absent.

Watercore; Slightly apparent.

Fruit cracking: None.

Culture: The shape and uniformity of the fruit shows a tendency todisperse, but these problems can be solved by usual fruit thinningmethods.

The cultivar "Nijisseiki" is widely cultivated, and its seedling iseasily available in Japan.

SUMMARY OF THE INVENTION

This new cultivar of Japanese pear tree "Gold Nijisseiki" has a strongvigor, a strong trunk and a short internode, a high productivity and ahigh quality fruit, and thus the characteristics of the tree aresubstantially the same as those of "Nijisseiki", except that the present"Gold Nijisseiki" has a significantly strong resistance to black spotdisease, and flowering time, is a few days earlier than "Nijisseiki".The present tree has an affinity to "Chojuro", "Kosui" etc. inconnection with pollination. The tree has a width of about 7 meters andheight of about 2.5 meters when the tree is treated with trellistraining to a height of about 1.8 meters. The tree has medium branchinghabits and medium branch density when unpruned. When the tree isconventionally treated with trellis training and pruned, vegetativeshoots and succulent spouts grow well, and further, the tree canopydevelops quickly. When a ten year old tree was cultivated in the centralpart of the Kanto district, e.g., Ibaraki prefecture, Japan, avegetative shoot was extended by 70-80 cm, on average. The crotch anglesformed by branches are about 47 degrees. The tree produces around-shaped fruit that matures in the middle of the season, e.g., fromthe middle to the end of September, in the central part of Kantodistinct, Japan.

The fruit has a medium size, i.e., 300-350 g, a yellowish-green skin,and yellowish-white flesh that is soft and a moderate texture. The fruitjuice has a moderate Brix, and moderate acidity at a pH of about 4.47.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a photograph of a shape of the new cultivar of Japanese peartree "Gold Nijisseiki";

FIG. 2 is a photograph of adult leaves, the upper row being adaxial ofthe new cultivar of Japanese pear tree;

FIG. 3 is a photograph of adult leaves, the lower one being abaxial ofthe new cultivar of Japanese pear tree;

FIG. 4 is a photograph of the flower in the bud stage of the newcultivar of Japanese pear;

FIG. 5 is a photograph of the flower of the new cultivar of Japanesepear tree;

FIG. 6 is a photograph of the side of fruit of the new cultivar ofJapanese pear tree;

FIG. 7 is a photograph of views at the blossom end of fruit of the newcultivar of Japanese pear tree;

FIG. 8 is a photograph of views at the stem end of fruit of the newcultivar of Japanese pear tree;

FIG. 9 is a photograph of cross-sectional view of fruit of the newcultivar of Japanese pear tree; and

FIG. 10 is a photograph of longitudinal-sectional view of fruit of thenew cultivar of Japanese pear tree.

DESCRIPTION OF THE CULTIVAR

The characteristics of the new and distinct cultivar of Japanese peartree "Gold Nijisseiki" are as follows:

Tree:

Vigor.--Habit of branches is medium. The unpruned tree may have a heightof about 7 m and a width of about 4 m when 15 years old. When the treewas grafted on a root stock, which is a seedling stock of Japanese pear,and cultivated for 10 years, a vegetative shoot of the tree extended to70-80 cm per year.

Spur.--Easy to maintain. The number of spurs is 12 per meter of branch.

Predominance of axillary flower bud.--Few (7.4%).

Time of bud break.--Middle, around April 7th, at the Institute ofRadiation Breeding, NIAR, Japan.

Production.--High productivity.

Cross-compatibility.--Cross-compatible with, e.g., "Chojuro", "Kosui".The tree is self-incompatible and is manually pollinated. The fruit setpercentage is 90-100%.

Bark.--The bark texture of the new and old wood is hard, and the bark ofa 10 year old tree may be cracked. The lenticels of the new and old woodare medium, and density thereof is medium (122 lenticels/10 cm).

Branches (shoot):

Length.--Medium, about 73.1 cm at one year old.

Thickess.--Stout, about 9.05 mm.

Length of internode.--Short, about 4.3 cm.

Color.--Light green brown (ISCC-NBS, Strong Yellowish Brown).

Density of pubescence.--High.

Angle between leaf bud and shoot.--Medium, about 26.0°.

Leaves:

Shape.--Oval.

Size.--Medium (11.2 cm×6.9 cm).

Color.--Dark Green (ISCC-NBS, Dark Green).

Length of petiole.--Short, about 2.5 cm.

Thickness of petiole.--Medium, about 2.4 mm.

Color of young leaves.--Brown (ISCC-NBS, Deep Reddish Brown).

Density of pubescence of young leaves.--High.

Flowers:

Flower number in a flower cluster.--Slightly more than medium, about9.65 on average.

Size.--Medium, about 3.4 cm.

Color.--Light pink (ISCC-NBS, Light Pink) calyx, coloration at bloomingfades to pure white (ISCC-NBS, White) with flower opening.

Shape of petals.--Round.

Notch of margin of petals.--Medium.

Number of petals.--Slightly more than medium, 5.54 pieces on average.

Color of anther.--Strong red (ISCC-NBS, Strong Red).

Number of stamens.--Slightly more than medium, 26.2 on average.

Number of pollen.--Much.

Flowering time.--Middle in the season.

Flowering date and full bloom stage.--April 19th and April 22th at theInstitute of Radiation Breeding, NIAR, on average from 1987 to 1989.

Fruit:

Size.--325 g on average.

Shape.--Round.

Color of skin (unbagged fruit).--Yellowish green (NSCC-NBS, Light YellowGreen).

Calyx perpetual fruit.--Absent.

Size of dot.--Medium.

Density of dot.--Medium.

Color of flesh.--Yellowish white (ISCC-NBS, Pale Greenish Yellow).

Flesh.--Soft and juicy. The firmness is about 4.03 lbs. according toMagness-Teller's hardness meter index. The fruit can be stored at20°-25° C. for 15 days.

Length of peduncle.--Medium, 3.1 cm on average.

Thickness of peduncle.--Stout, 3.8 mm on average.

Color of peduncle.--Dull green (ISCC-NBS, Moderate Yellowish Green).

Color of dot.--Dull green (ISCC-NBS, Moderate Yellow).

Color of core.--Yellowish white (ISCC-NBS, Yellowish White).

Shape of core.--Short conical.

Size of core.--Medium (core/fruit=38/89, at transverse diameter).

Seed cells.--5 cells per fruit, about 1.7 seeds per cell, 4-5 seeds perwell shaped fruit.

Size of seeds.--Medium, 9.0 mm×5.7 mm on average.

Shape of seeds.--Oval.

Taste.--Moderate sweetness, the sugar content of the fruit juice isabout 10.3%, a medium acidity, pH 4.47, and no astringency. Although thetaste of the fruit at skin/fresh interface cannot be distinguished, thetaste of the core flesh tissues surrounding the seed cells has slightlyhigher acidity than other parts.

Bagged.--The bagged fruit has a slightly fine appearance compared tofruit that has not been bagged, but the latter is less than the formerin sweetness. Color of both are not distinguishable from each other, butin the unbagged fruit cork spots are slightly more apparent than in thebagged fruit.

Maturity.--Ripening middle in the season, e.g., September 16-25th at theInstitute of Radiation Breeding, NIAR.

Use.--Suitable for dessert.

Keeping quality.--Can be kept for about 15 days at 20°-25° C.

Resistance to diseases: In a test using a spore of Alternariakikuchiana, which is pathogenic fungi that induces Black spot disease,in the laboratory, a resistant cultivar "Chojuro" developed symptoms forabout 20% of the second leaves, thereafter the symptoms decreasing ordisappearing as leaf age increases, while "Nijisseiki" was 100% diseasedin the second through fifth leaves. When inoculated with the spores, thepresent tree "Gold Nijisseiki" developed symptoms for about 80% andabout 17% of the second and third leaves, respectively, but the fourthor greater leaves displayed no symptoms. As a result, it is confirmedthat although the present tree "Gold Nijisseiki" has a slightly lowerresistance to black spot disease than the tree "Chyojuro", the presenttree has a significantly higher resistance to black spot disease thanthe parent tree "Nijisseiki". In field cultivation, the present treesdid not develop the similar symptoms when subjected to the same controlmethods for black spot disease as those applied to the resistantcultivar, and if there were symptoms, the lesion of the leaves did notextend, and only the lesion part, which was dried and grayish brown incolor, was deleted from the leaf. Thus, the present tree did not sufferfrom leaf abscission as much as "Nijisseiki". Furthermore, 60% of theyoung fruit of "Nijisseiki" experienced cracking. In contrast, there wasscarcely no disease or injury on the present tree. The present tree hassusceptibility to pear necrotic spot virus, and has minor susceptibilityto pear scab. The tree is not susceptible to pear canker.

Cold resistant: Almost the same as that of other Japanese pears.

Core breakdown: Absent.

Watercore: Slightly observed.

Fruit cracking: None.

Culture: The shape and uniformity of the fruit shows a tendency todisperse, but these problems can be solved by usual fruit thinningmethods.

The new cultivar of Japanese pear tree "Gold Nijisseiki" is cultivatedand kept at the Institute of Radiation Breeding, National Institute ofAgrobiological Resources, Omiya-machi, Naka-gun, Ibaraki, Japan.

Since the new cultivar, "Gold Nijisseiki", has a strong resistance toblack spot disease, and has excellent dessert quality, etc., the treesof the present cultivar can be conveniently and easily cultivated invarious agricultural districts.

We claim:
 1. A new and distinct cultivar of Japanese pear tree bearing ayellowish green fruit, substantially as herein illustrated anddescribed, characterized by its vigorous, medium growth and its abilityto produce a medium size fruit having soft, yellowish white flesh thatflowers about 2 days earlier than "Nijisseiki", and has a significantlystrong resistance to black spot disease compared to "Nijisseiki"; thefruit is further characterized by its good taste which is moderatelysweet and acidic, and its keeping quality.